Eight speed dual clutch transmission

ABSTRACT

A transmission is connectable to an input member and includes an output transfer gear, first and second shaft members, first and second countershaft members, a plurality of co-planar gear sets, and a plurality of torque transmitting devices. The torque transmitting devices include a plurality of gears, synchronizer assemblies and a dual clutch assembly. The transmission is operable to provide at least one reverse speed ratio and a plurality of forward speed ratios between the input member and the output member.

TECHNICAL FIELD

The present disclosure relates to transmissions and more particularly toa compact, dual clutch multiple speed transmission having at least twocountershafts to establish eight or more gear speeds.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission having countershafts and co-planargear sets uses countershaft gears with a different, dedicated gear pairor set to achieve each forward speed ratio. Accordingly, the totalnumber of gears required in this typical design is two times the numberof forward speeds, plus three for reverse. This necessitates a largenumber of required gear pairs, especially in transmissions that have arelatively large number of forward speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needin the art for a transmission having improved packaging while providingdesirable gear ratios and torque ranges.

SUMMARY

The present invention provides a transmission is connectable to an inputmember and includes an output member, first and second shaft members,first and second countershaft members, a plurality of co-planar gearsets, and a plurality of torque transmitting devices. The torquetransmitting devices include a plurality of synchronizer assemblies anda dual clutch assembly. The transmission is operable to provide at leastone reverse speed ratio and a plurality of forward speed ratios betweenthe input member and the output member.

In another aspect of the present invention, the transmission includes atransmission housing.

In another aspect of the present invention, the transmission includes adual clutch assembly having a first clutch, second clutch, and a clutchhousing connectable to an engine output member. The clutch housing isrotationally supported within the transmission housing.

In another aspect of the present invention, the transmission includes afirst, second, third, fourth, fifth and sixth gear set. The first gearset includes a first gear in mesh with a second gear and a third gear.The second gear set includes a first gear in mesh with a second gear anda third gear. The third gear set includes a first gear in mesh with asecond gear. The fourth gear set includes a first gear in mesh with asecond gear. The fifth gear set includes a first gear in mesh with athird gear, and the third gear is in mesh with a second gear. The sixthgear set includes a first gear in mesh with a second gear and a thirdgear.

In another aspect of the present invention, the transmission includes afirst transmission input member rotatably supported in the transmissionhousing. Each of the first gears of the third, fourth, fifth and sixthgear sets are rotatably fixed for common rotation with the firsttransmission input member. The selective engagement of the first clutchof the dual clutch assembly transfers torque from the clutch housing tothe first transmission input member.

In another aspect of the present invention, the transmission includes asecond transmission input member rotatably supported in the transmissionhousing. Each of first gears of the first and second gear sets arerotatably fixed for common rotation with the second transmission inputmember. The second transmission input member is concentric with thefirst transmission input member and at least partially surrounds thefirst transmission input member. The selective engagement of the secondclutch of the dual clutch assembly transfers torque form the clutchhousing to the second transmission input member.

In another aspect of the present invention, the transmission includes afirst countershaft rotatably supported within the transmission housingand spaced apart from and parallel with the first and secondtransmission input members. The third gear of the first gear set, thethird gear of the second gear set and the third gear of the sixth gearset are each selectively connectable for common rotation with the firstcountershaft. The third gear of the fifth gear set is supported for freerotation on the first countershaft.

In another aspect of the present invention, the transmission includes asecond countershaft rotatably supported within the transmission housingand spaced apart from and parallel with the first and secondtransmission input members. The second gear of the first gear set, thesecond gear of the second gear set, the second gear of the third gearset, the second gear of the fourth gear set, the second gear of thefifth gear set and the second gear of the sixth gear set are eachselectively connectable for common rotation with the secondcountershaft.

In another aspect of the present invention, the transmission includesfive synchronizer assemblies for selectively coupling at least one ofthe gears of the first, second, third, fourth, fifth and sixth gear setswith at least one of the first countershaft and the second countershaft.

In another aspect of the present invention, the selective engagement ofthe first and second clutches of the dual clutch assembly interconnectsthe dual clutch housing with at least one of the first and the secondtransmission input members and the selective engagement of at least oneof the five synchronizer assemblies establishes at least one of eightforward speed ratios.

The above features and advantages and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings wherein like referencenumbers refer to the same component, element or feature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an embodiment of an eight speedtransmission having a dual clutch, two input shafts, a plurality of gearsets and a plurality of synchronizers, in accordance with the presentinvention.

DESCRIPTION

Referring to FIG. 1, a multiple speed transmission is generallyindicated by reference number 10. The transmission 10 is connectable toan input member 12 and has an output member or gear 14. In the presentembodiment, the input member 12 is a shaft and the output member 14 is agear, however those skilled in the art will appreciate that the inputmember 12 may be components other than shafts and the output member 14may be a component, such as a shaft, other than a gear.

The input member 12 is continuously connected with an engine 16 or othertorque producing machine to provide a driving torque to input member 12.The output member or gear 14 rotatably drives a differential assembly18. The differential assembly 18 transfers torque delivered by outputmember 14, ultimately, to a pair road wheels (not shown).

The transmission 10 includes a housing 19 that at least partiallyencloses a gearing arrangement 20. The gearing arrangement 20 includesvarious shafts or members, co-planar intermeshing gear sets, a dualclutch assembly, and selectively engageable synchronizers, as will bedescribed herein. For example, the gearing arrangement 20 includes afirst transmission input shaft or member 22, a second transmission inputshaft or member 24, a first countershaft 26, and a second countershaft28. The second transmission input shaft or member 24 is a hollow shaftthat is concentric with and overlies the first transmission input shaftor member 22. The first countershaft 26 and the second countershaft 28are each spaced apart from and parallel with the first and secondtransmission input shaft members 22, 24. The first and secondtransmission input shafts 22, 24 define a first axis of rotation, thefirst countershaft 26 defines a second axis of rotation and the secondcountershaft 28 defines a third axis of rotation. The position andlocation of countershafts 26 and relative to first and secondtransmission input shafts 22, 24 are interchangeable.

A dual clutch assembly 32 is connectable between the input member 12 andthe first and second transmission input shaft members 22, 24. The dualclutch assembly 32 includes a clutch housing 34 connectable for commonrotation with the input member 12. Further, the dual clutch assembly 32has first and second clutch elements or hubs 36 and 38. Clutch elements36 and 38 together with the clutch housing 34 are configured to form afriction clutch, as is known in the art as a dual clutch. Morespecifically, clutch elements 36, 38 and the clutch housing 34 havefriction plates mounted thereon or otherwise coupled thereto thatinteract to form a friction clutch. The clutch element 36 is connectedfor common rotation with the first transmission input shaft or member 22and the clutch element 38 is connected for common rotation with thesecond transmission input shaft or member 24. Thus, selective engagementof clutch element 36 with the clutch housing 34 connects the inputmember 12 for common rotation with the first transmission input shaftmember 22. Selective engagement of clutch element 38 with the clutchhousing 34 connects the input member 12 for common rotation with thesecond transmission input shaft member 24. It should be appreciated thatwhile the dual clutch assembly 32 is shown throughout the FIGURE as awet clutch assembly, the dual clutch assembly 32 may be a dry clutchassembly without departing from the scope of the present invention.

The gearing arrangement 20 also includes a plurality of co-planar,meshing gear sets 40, 50, 60, 70, 80 and 90. The present inventioncontemplates that the plurality of co-planar, meshing gear sets 40, 50,60, 70, 80 and 90 may be arranged axially along transmission inputshafts 22, 24 in an order other than that which is shown in FIG. 1 andstill be within the scope of the invention. Co-planar gear set 40includes first pinion gear 42, second pinion gear 44 and third piniongear 46. First pinion gear 42 is rotatably fixed and connected forcommon rotation with the second transmission input shaft member 24.Second pinion gear 44 is selectively connectable for common rotationwith the second countershaft member 28 and meshes with first pinion gear42. Third pinion gear 46 is selectively connectable for common rotationwith the first countershaft member 26 and meshes with first pinion gear42. It should be appreciated that first pinion gear 42 may be a separategear structure fixed to the second transmission input shaft member 24 orgear teeth/splines formed on an outer surface of the second transmissioninput shaft member 24 without departing from the scope of the presentinvention. Gear set 40 is disposed proximate a wall 48 of thetransmission housing 19 that is on a front or side of the transmission10 proximate the dual clutch assembly 32.

Co-planar gear set 50 includes first pinion gear 52, second pinion gear54 and third pinion gear 56. First pinion gear 52 is rotatably fixed andconnected for common rotation with the second transmission input shaftmember 24 and meshes with second pinion gear 54 and third pinion gear56. Second pinion gear 54 is selectively connectable for common rotationwith the second countershaft member 28. Third pinion gear 56 isselectively connectable for common rotation with the first countershaftmember 26. Gear set 50 is positioned adjacent gear set 40.

Co-planar gear set 60 includes first pinion gear 62 and second piniongear 64. First pinion gear 62 is rotatably fixed and connected forcommon rotation with the first transmission input shaft member 22 andmeshes with second pinion gear 64. Second pinion gear 64 is selectivelyconnectable for common rotation with the second countershaft member 28.Gear set 60 is disposed adjacent gear set 50.

Co-planar gear set 70 includes first pinion gear 72 and second piniongear 74. First pinion gear 72 is rotatably fixed and connected forcommon rotation with the first transmission input shaft member 22 andmeshes with second pinion gear 74. Second pinion gear 74 is selectivelyconnectable for common rotation with the second countershaft member 28.Gear set 70 is positioned adjacent gear set 60.

Co-planar gear set 80 includes first pinion gear 82, second pinion gear84 and third pinion gear 86. First pinion gear 82 is rotatably fixed andconnected for common rotation with the first transmission input shaftmember 22 and meshes with third pinion gear 86. Third pinion gear 86 isfree to rotate on the first countershaft member 26 and meshes withsecond pinion gear 84. Second pinion gear 84 is selectively connectablefor common rotation with the second countershaft member 28. Gear set 80is positioned adjacent gear set 70.

Co-planar gear set 90 includes first pinion gear 92, second pinion gear94 and third pinion gear 96. First pinion gear 92 is rotatably fixed andconnected for common rotation with the first transmission input shaftmember 22 and meshes with second pinion gear 94 and third pinion gear96. Second pinion gear 94 is selectively connectable for common rotationwith the second countershaft member 28. Third pinion gear 96 isselectively connectable for common rotation with the first countershaftmember 26. Gear set 90 is positioned between gear set 80 and an end wall98 of the transmission housing 19.

Further, a first countershaft transfer gear 100 is rotatably fixed andconnected for common rotation with the first countershaft member 26. Asecond countershaft transfer gear 110 is rotatably fixed and connectedfor common rotation with the second countershaft member 28. Firstcountershaft transfer gear 100 is configured to mesh with output member14 and the second countershaft transfer gear 110 is configured to meshwith output member 14. However, the first countershaft transfer gear 100and the second countershaft transfer gear 110 do not mesh with eachother.

A park gear (not shown) may be provided for placing transmission 10 in apark mode that prevents output member 14 from rotating. The park gearmay be rotationally fixed to the first countershaft member 26 or to thesecond countershaft member 28. However, the axial location of the parkgear along the first or second countershaft members 26, 28 may bechanged in accordance with available packaging space.

With continued reference to FIG. 1, the transmission 10 further includesa plurality of selectively engageable synchronizer assemblies 150, 152,154, 156 and 158. Synchronizers 150, 152, 154 and 156 are double sidedsynchronizers and generally include a shift fork (not shown) that isbi-directionally translated by an actuator (not shown) into at least twoengaged positions and a neutral or disengaged position. In the presentembodiment, synchronizer 150 is selectively actuatable to connect gear44 for common rotation with the second countershaft member 28 and isselectively actuatable to connect gear 54 for common rotation with thesecond countershaft member 28. Synchronizer 152 is selectivelyactuatable to connect for common rotation gear 46 with the firstcountershaft member 26 and is selectively actuatable to connect forcommon rotation gear 56 with the first countershaft member 26.Synchronizer 154 is selectively actuatable to connect for commonrotation gear 64 with the second countershaft 28 and is selectivelyactuatable to connect for common rotation gear 74 with the secondcountershaft member 28. Synchronizer 156 is selectively actuatable toconnect for common rotation gear 84 with the second countershaft 28 andis selectively actuatable to connect for common rotation gear 94 withthe second countershaft member 28. Synchronizer 158 is a single sidedsynchronizer and generally includes a shift fork (not shown) that isbi-directionally translated by an actuator (not shown) into at least oneengaged position and a neutral or disengaged position. Synchronizer 158is selectively actuatable to connect for common rotation gear 96 withthe first countershaft member 26.

The transmission 10 is capable of transmitting torque from the inputshaft 12 to the output gear member 14 in at least eight forward torqueratios and at least one reverse torque ratio. Each of the forward torqueratios and the reverse torque ratio is attained by selective engagementof the dual clutch assembly 32 and one or more of the synchronizerassemblies 150, 152, 154, 156 and 158. Those skilled in the art willreadily understand that a different speed ratio is associated with eachtorque ratio.

It should be appreciated that each individual gear set 40, 50, 60, 70,80 and 90 provides one or more forward and/or reverse gear ratios uponselective engagement of the synchronizer assemblies 150, 152, 154, 156and 158. It should also be appreciated that a particular forward orreverse speed ratio may be achieved by different combinations ofsynchronizer and associated gear sets without departing from the scopeof the present invention.

For example, to establish the reverse torque ratio, clutch element 36 isengaged and synchronizer 156 is activated. Clutch element 36 couples theinput member 12 with the first transmission input shaft member 22.Synchronizer 156 connects gear 84 to the second countershaft member 28.More specifically, input torque from the input shaft 12 is transferredthrough the dual clutch assembly 32 to the first transmission inputshaft member 22, through pinion gear 82 to gear 86, through gear 86 togear 84, from gear 84 to the second countershaft member 28 throughsynchronizer 156, then to second countershaft transfer gear 110 and fromsecond countershaft transfer gear 110 to the output member 14.

To establish a first forward torque ratio (i.e. a 1st gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 with the first transmission input shaftmember 22. Synchronizer 154 couples gear 64 to the second countershaftmember 28. Input torque from the input member 12 is transferred throughthe dual clutch assembly 32 to the first transmission input shaft member22 to pinion 62. Pinion 62 transfers torque to gear 64 which transfersthe torque to the second countershaft member 28 through synchronizer 154and from the second countershaft member 28 to second countershafttransfer gear 110 and then from second countershaft transfer gear 110 tothe output member 14.

To establish a second forward torque ratio (i.e. a 2nd gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 42. Synchronizer 150 couples gear 44 tothe second countershaft member 28. Accordingly, input torque from theinput member 12 is transferred through the dual clutch assembly 32 tothe second transmission input shaft member 24, through pinion 42 to gear44, from gear 44 to synchronizer 150, from synchronizer 150 to thesecond countershaft member 28 and from the second countershaft member 28to the second countershaft transfer gear 110 and the output member 14.

To establish a third forward torque ratio (i.e. a 3rd gear), clutchelement 36 is engaged and synchronizer 154 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 72. Synchronizer 154 couples gear 74 tothe second countershaft member 28. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thefirst transmission input shaft member 22, through pinion 72 to gear 74,through gear 74 to synchronizer 154, from synchronizer 154 to the secondcountershaft member 28, from the second countershaft member 28 to thesecond countershaft transfer gear 110 and then from second countershafttransfer gear 110 to the output member 14.

To establish a fourth forward torque ratio (i.e. a 4th gear), clutchelement 38 is engaged and synchronizer 152 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 42. Synchronizer 152 couples gear 46 tothe first countershaft member 26. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thesecond transmission input shaft member 24 to pinion 42, then from pinion42 to gear 46, from gear 46 to synchronizer 152, from synchronizer 152to the first countershaft member 26, from the first countershaft member26 to first countershaft transfer gear 100 and then from firstcountershaft transfer gear 100 to the output member 14.

To establish a fifth forward torque ratio (i.e. a 5th gear), clutchelement 36 is engaged and synchronizer 156 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 92. Synchronizer 156 couples gear 94 tothe second countershaft member 28. Input torque from the input member 12is transferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, from first transmission input shaftmember 22 to pinion 92, from pinion 92 to gear 94, from gear 94 to thesecond countershaft member 28 through synchronizer 156 to secondcountershaft transfer gear 110 and from second countershaft transfergear 110 to the output member 14.

To establish a sixth forward torque ratio (i.e. a 6th gear), clutchelement 38 is engaged and synchronizer 150 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 52. Synchronizer 150 couples gear 54 tothe second countershaft member 28. Thus, input torque from the inputmember 12 is transferred through the dual clutch assembly 32 to thesecond transmission input shaft member 24 to pinion 52, then from pinion52 to gear 54, from gear 54 to synchronizer 150, from synchronizer 150to the second countershaft member 28, from the second countershaftmember 28 to second countershaft transfer gear 110 and then from secondcountershaft transfer gear 110 to the output member 14.

To establish a seventh forward torque ratio (i.e. a 7th gear), clutchelement 36 is engaged and synchronizer 158 is activated. Clutch element36 couples the input member 12 to the first transmission input shaftmember 22 which rotates pinion 92. Synchronizer 158 couples gear 96 tothe first countershaft member 26. Input torque from the input member 12is transferred through the dual clutch assembly 32 to the firsttransmission input shaft member 22, from first transmission input shaftmember 22 to pinion 92, from pinion 92 to gear 96, from gear 96 to thefirst countershaft member 26 through synchronizer 158 to firstcountershaft transfer gear 100 and from first countershaft transfer gear100 to the output member 14.

To establish an eighth forward torque ratio (i.e. an 8th gear), clutchelement 38 is engaged and synchronizer 152 is activated. Clutch element38 couples the input member 12 to the second transmission input shaftmember 24 which rotates pinion 52. Synchronizer 152 couples gear 56 tothe first countershaft member 26. Input torque from the input member 12is transferred through the dual clutch assembly 32 to the secondtransmission input shaft member 24, from second transmission input shaftmember 24 to pinion 52, from pinion 52 to gear 56, from gear 56 to thefirst countershaft member 26 through synchronizer 152 to firstcountershaft transfer gear 100 and from first countershaft transfer gear100 to the output member 14.

Again, it should be appreciated that any one of the gear sets of gearsets 40, 50, 60, 70, 80 and 90 may be changed in size and number gearteeth or gear pitch to produce a certain forward and reverse torqueratio without departing from the scope of the present invention.

The present invention contemplates that a variety of torque ratios(i.e., the ratio of torque of the output member 14 to the input member12) and ratio steps are achievable through the selection of tooth countsof the gears of the transmission 10. The present invention has manyadvantages and benefits over the prior art. For example, the presentconfiguration allows for high overall ratio spreads between the firstgear ratio and the eighth gear ratio by employing separate pinion gearsfor the first gear ratio and the eighth gear ratio. In addition, thelength of the transmission 10 in the area of the first countershaftmember 26 is reduced thereby limiting interference with othertransmission components. Thus, a transmission having a more simplifiedactuation and control system, reduced mass and cost and improvedpackaging is achieved.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

The invention claimed is:
 1. A transmission comprising: a transmissionhousing; a dual clutch assembly having a first clutch, second clutch anda clutch housing connectable to an engine output member, wherein theclutch housing is rotationally supported within the transmissionhousing; a first, second, third, fourth, fifth and sixth gear set,wherein the first gear set includes a first gear in mesh with a secondgear and a third gear, the second gear set includes a first gear in meshwith a second gear and a third gear, the third gear set includes a firstgear in mesh with a second gear, the fourth gear set includes a firstgear in mesh with a second gear, the fifth gear set includes a firstgear in mesh with a third gear, wherein the third gear is in mesh with asecond gear and the sixth gear set includes a first gear in mesh with asecond gear and a third gear; a first transmission input memberrotatably supported in the transmission housing and wherein each of thefirst gears of the third, fourth, fifth and sixth gear sets arerotatably fixed for common rotation with the first transmission inputmember and wherein the selective engagement of the first clutch of thedual clutch assembly transfers torque from the clutch housing to thefirst transmission input member; a second transmission input memberrotatably supported in the transmission housing and wherein each of thefirst gears of the first and second gear sets are rotatably fixed forcommon rotation with the second transmission input member and whereinthe second transmission input member is concentric with the firsttransmission input member and at least partially surrounds the firsttransmission input member and wherein the selective engagement of thesecond clutch of the dual clutch assembly transfers torque form theclutch housing to the second transmission input member; a firstcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members, wherein the third gear of the first gear set, the thirdgear of the second gear set and the third gear of the sixth gear set areeach selectively connectable for common rotation with the firstcountershaft, and wherein the third gear of the fifth gear set issupported for free rotation on the first countershaft; a secondcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members, wherein the second gear of the first gear set, the secondgear of the second gear set, the second gear of the third gear set, thesecond gear of the fourth gear set, the second gear of the fifth gearset and the second gear of the sixth gear set are each selectivelyconnectable for common rotation with the second countershaft; and fivesynchronizer assemblies for selectively coupling at least one of thegears of the first, second, third, fourth, fifth and sixth gear setswith at least one of the first countershaft and the second countershaft,and wherein the selective engagement of the first and second clutches ofthe dual clutch assembly interconnects the dual clutch housing with atleast one of the first and the second transmission input members and theselective engagement of at least one of the five synchronizer assembliesestablishes at least one of eight forward speed ratios.
 2. Thetransmission of claim 1 wherein a first of the five synchronizerassemblies selectively connects at least one of the second gear of thefirst gear set and the second gear of the second gear set to the secondcountershaft.
 3. The transmission of claim 2 wherein a second of thefive synchronizer assemblies selectively connects at least one of thethird gear of the first gear set and third gear of the second gear setto the first countershaft.
 4. The transmission of claim 3 wherein athird of the five synchronizer assemblies selectively connects at leastone of the second gear of the third gear set and the second gear of thefourth gear set to the second countershaft.
 5. The transmission of claim4 wherein a fourth of the five synchronizer assemblies selectivelyconnects at least one of the second gear of the fifth gear set andsecond gear of the sixth gear set to the second countershaft.
 6. Thetransmission of claim 5 wherein a fifth of the five synchronizerassemblies selectively connects the third gear of the sixth gear set tothe first countershaft.
 7. The transmission of claim 1 wherein the firstgear set is adjacent the dual clutch assembly, the second gear set isadjacent the first gear set, the third gear set is adjacent the secondgear set, the fourth gear set is adjacent the third gear set, the fifthgear set is adjacent the fourth gear set and the sixth gear set isdisposed between the fifth gear set and an end wall of the transmissionhousing.
 8. The transmission of claim 7 wherein the five synchronizerassemblies includes a first synchronizer assembly for selectivelyconnecting the second gear of the first gear set to the secondcountershaft to establish a second gear ratio when the second clutch ofthe dual clutch is engaged to connect the dual clutch housing to thesecond transmission input member.
 9. The transmission of claim 8 whereinthe five synchronizer assemblies includes a first synchronizer assemblyfor selectively connecting the second gear of the second gear set to thesecond countershaft to establish a sixth gear ratio when the secondclutch of the dual clutch is engaged to connect the dual clutch housingto the second transmission input member.
 10. The transmission of claim 9wherein the five synchronizer assemblies includes a second synchronizerassembly for selectively connecting the third gear of the first gear setto the first countershaft to establish a fourth gear ratio when thesecond clutch of the dual clutch is engaged to connect the dual clutchhousing to the second transmission input member.
 11. The transmission ofclaim 10 wherein the five synchronizer assemblies includes a secondsynchronizer assembly for selectively connecting the third gear of thesecond gear set to the first countershaft to establish an eighth gearratio when the second clutch of the dual clutch is engaged to connectthe dual clutch housing to the second transmission input member.
 12. Thetransmission of claim 11 wherein the five synchronizer assembliesincludes a third synchronizer assembly for selectively connecting thesecond gear of the third gear set to the second countershaft toestablish a first gear ratio when the first clutch of the dual clutch isengaged to connect the dual clutch housing to the first transmissioninput member.
 13. The transmission of claim 12 wherein the fivesynchronizer assemblies includes a third synchronizer assembly forselectively connecting the second gear of the fourth gear set to thesecond countershaft to establish a third gear ratio when the firstclutch of the dual clutch is engaged to connect the dual clutch housingto the first transmission input member.
 14. The transmission of claim 13wherein the five synchronizer assemblies includes a fourth synchronizerassembly for selectively connecting the second gear of the fifth gearset to the second countershaft to establish a reverse gear ratio whenthe first clutch of the dual clutch is engaged to connect the dualclutch housing to the first transmission input member.
 15. Thetransmission of claim 14 wherein the five synchronizer assembliesincludes a fourth synchronizer assembly for selectively connecting thesecond gear of the sixth gear set to the second countershaft toestablish a fifth gear ratio when the first clutch of the dual clutch isengaged to connect the dual clutch housing to the first transmissioninput member.
 16. The transmission of claim 15 wherein the fivesynchronizer assemblies includes a fifth synchronizer assembly forselectively connecting the third gear of the sixth gear set to the firstcountershaft to establish a seventh gear ratio when the first clutch ofthe dual clutch is engaged to connect the dual clutch housing to thefirst transmission input member.
 17. The transmission of claim 1 furthercomprising a first countershaft transfer gear fixed to the firstcountershaft for common rotation with the first countershaft and asecond countershaft transfer gear fixed to the second countershaft forcommon rotation with the second countershaft and wherein the first andsecond countershaft transfer gears transfer torque from at least one ofthe first and second countershafts to a transmission output member. 18.The transmission of claim 17 wherein the transmission output member is agear that meshes with the each of the first and second countershafttransfer gears.
 19. A transmission comprising: a transmission housing; adual clutch assembly having a first clutch, second clutch, and a clutchhousing connectable to an engine output member, wherein the clutchhousing is rotationally supported within the transmission housing; afirst, second, third, fourth, fifth and sixth gear set, wherein thefirst gear set includes a first gear in mesh with a second gear and athird gear, the second gear set includes a first gear in mesh with asecond gear and a third gear, the third gear set includes a first gearin mesh with a second gear, the fourth gear set includes a first gear inmesh with a second gear, the fifth gear set includes a first gear inmesh with a third gear, wherein the third gear is in mesh with a secondgear and the sixth gear set includes a first gear in mesh with a secondgear and a third gear; a first transmission input member rotatablysupported in the transmission housing and wherein each of the firstgears of the third, fourth, fifth and sixth gear sets are rotatablyfixed for common rotation with the first transmission input member andwherein the selective engagement of the first clutch of the dual clutchassembly transfers torque from the clutch housing to the firsttransmission input member; a second transmission input member rotatablysupported in the transmission housing and wherein each of the firstgears of the first and second gear sets are rotatably fixed for commonrotation with the second transmission input member and wherein thesecond transmission input member is concentric with the firsttransmission input member and at least partially surrounds the firsttransmission input member and wherein the selective engagement of thesecond clutch of the dual clutch assembly transfers torque form theclutch housing to the second transmission input member; a firstcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members, wherein the third gear of the first gear set, the thirdgear of the second gear set and the third gear of the sixth gear set areeach selectively connectable for common rotation with the firstcountershaft, and wherein the third gear of the fifth gear set issupported for free rotation on the first countershaft; a secondcountershaft rotatably supported within the transmission housing andspaced apart from and parallel with the first and second transmissioninput members, wherein the second gear of the first gear set, the secondgear of the second gear set, the second gear of the third gear set, thesecond gear of the fourth gear set, the second gear of the fifth gearset and the second gear of the sixth gear set are each selectivelyconnectable for common rotation with the second countershaft; a firstsynchronizer assembly selectively connects at least one of the secondgear of the first gear set and the second gear of the second gear set tothe second countershaft; a second synchronizer assembly selectivelyconnects at least one of the third gear of the first gear set and thirdgear of the second gear set to the first countershaft; a thirdsynchronizer assembly selectively connects at least one of the secondgear of the third gear set and the second gear of the fourth gear set tothe second countershaft; a fourth synchronizer assembly selectivelyconnects at least one of the second gear of the fifth gear set andsecond gear of the sixth gear set to the second countershaft; a fifthsynchronizer assembly selectively connects the third gear of the sixthgear set to the first countershaft; and a first countershaft transfergear fixed to the first countershaft for common rotation with the firstcountershaft and a second countershaft transfer gear fixed to the secondcountershaft for common rotation with the second countershaft andwherein the first and second countershaft transfer gears transfer torquefrom at least one of the first and second countershafts to atransmission output member, and wherein the selective engagement of thefirst and second clutches of the dual clutch assembly and the selectiveengagement of at least one of the synchronizer assemblies establishes atleast one of eight forward speed ratios between the at least one of thefirst and the second transmission input members and the transmissionoutput member.